When the channel state between an evolved Node B (eNB) and a User Equipment (UE) is poor, an RN may be installed between them to thereby provide a radio channel in a better channel state to the UE. In addition, with the introduction of an RN at a cell edge suffering a poor channel state from an eNB, a higher-rate data channel can be provided and cell coverage can be extended. The use of RNs is a widely used technology aiming to eliminate shadowing areas in wireless communication systems.
Compared to a conventional relay technology confined to the function of a repeater that simply amplifies a signal and forwards the amplified signal, the recent relay technology is more advanced. Further, the relay technology is essential to extend service coverage and increase data throughput as well as to reduce eNB installation cost and backhaul maintenance cost. Along with the development of the relay technology, RNs used in legacy wireless communication systems need to be supported in new wireless communication systems.
As an RN functions to forward a link connection between an eNB and a UE in a 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) system, two types of links having different characteristics are applied to each of uplink and downlink carrier frequency bands. A link established between the eNB and the RN is referred to as a backhaul link. When the backhaul link occupies downlink resources for Frequency Division Duplex (FDD) or Time Division Duplex (TDD) transmission, it is referred to as a backhaul downlink, whereas when the backhaul link occupies uplink resources for FDD or TDD transmission, it is referred to as a backhaul uplink.
To support relay-related link configurations, each of a legacy eNB and a legacy UE has one of a transmission module and a reception module for each of the uplink and the downlink. On the other hand, the RN needs to have both transmission and reception modules for each of the downlink and uplink.
Thus, the RN can transmit a signal to the eNB and receive a signal from the UE on the uplink. The RN can also receive a signal from the eNB and transmit a signal to the UE on the downlink. However, if the RN performs signal transmission and reception simultaneously, much interference and errors occur in many cases. Therefore, simultaneous transmission and reception at the RN is not preferred.
Accordingly, an appropriate timing is needed for the RN to exchange signals with the eNB and the UE. Nevertheless, no frame structure designed for signal exchange between an RN and an eNB and between the RN and a UE has been specified yet.